Some friends play sport together. Others drink beer, watch rugby and talk rubbish. Maybe you and your mates get together and dress up as zombies. Whatever floats your boat.
My friends like to debate things. Via email. These debates - they can range from the accents in the movie Troy to whether or not animated series The Clone Wars stays true to George Lucas' original Star Wars vision - can go on and on.
And on. Once it took us a chain of 57 emails just to organise a movie. Hey, some of us have kids.
Are we geeks? You betcha - but we're sorta cool geeks, and let's not forget, it's the geeks that rule this planet. I guess a geek would say that.
Our latest topic proved to be quite controversial and has been raging for about a week now. It was sparked by an issue of SFX magazine that put Blade Runner on top of a list of the 100 greatest science-fiction films ever made.
Talk about a putting a lit match to a petrol can. Over around 40-odd emails, heated discussions raged about the list, including arguments about the inclusion of Serenity (a movie based on a TV series), to whether or not Star Wars should be classified as a sci-fi film - or as science-fantasy.
Thankfully, sanity prevailed on that one. It may have freaking light sabres, but Star Wars has an emotional heart - an orphan's search for his half-robot father - that other films can only dream of.
After much arguing, sniping and occasional backstabbing, we each compiled our own top 10 lists, assigned points to each position, and collated the results to craft our own list of the Ultimate Definitive Top 10 Science-Fiction Films Ever Made.
Yes, some of my friends have far too much spare time on their hands. You should watch them while away days playing the Lord of the Rings version of Risk.
Anyway, here's our official top 10 (complete with ultra geeky comments on each film):
1. Star Wars: Episode V: Empire Strikes Back (1980): "Hypnotic, surreal, dreamlike with cinematography that is so outstanding."
2. Star Wars: Episode IV - A New Hope: (1977): "The most revolutionary movie ever with the best score ever."
3. The Matrix (1999): "The premise is very well thought-out and really trippy."
4. Alien (1979): "Creepy sci-fi horror, truly scary, truly great, very atmospheric."
5. 2001: A Space Odyssey (1968): "The benchmark for all sci-fi movies. Technically brilliant."
6. Gattaca (1997): "The most emotionally moving film in our Top 10. It's not an action movie, and there are no extra-terrestrials, but this is sci-fi at its most pure."
7. Blade Runner (1982): "There's something about the 'feel' of this movie. It's dreamlike and sad."
8. District 9 (2009): "One of few recent movies to make it on our top 10 ... original and moving."
8. Aliens (1986): "It never lets up, and you're sitting there in your living room fighting for your life against horrific alien enemies."
10. Terminator (1984): "The concept of this is absolutely brilliant ... and the scenes showing our prospective future are chilling".
* Next week we'll be debating the best Hugh Grant rom-coms of all time. But for now, post your own Top 10 Science-Fiction Films lists and comments below: